1. Field of the Invention
The present invention relates to a laminated electronic component and manufacturing method thereof, and more specifically to improvement of component reliability.
2. Description of the Related Art
Laminated electronic components, each formed by laminating multiple insulator layers with a pattern constituting a part of a coil conductor formed on the surface, and then connecting the patterns through via holes, thereby forming a spiral coil conductor, are utilized in various applications. Such laminated electronic components are facing the demand for component size reduction as the devices in which they are utilized become smaller, more power-efficient and higher-performance, and, in particular, laminated electronic components used as inductors in power circuits are asked to offer lower resistivity. The easiest way to reduce the resistance of a laminated electronic component is to increase the thickness of its internal conductor, and this method is adopted in many cases. At the same time, technologies to meet high reliability requirements are being examined and several methods have been proposed.
For example, the laminated electronic component described in Patent Literature 1 specified below employs the method of providing a larger land/via connection area so that stable connection can be achieved between the via and land of the laminated inductor even if the lamination accuracy in the vertical direction is poor. FIG. 7(C) shows a laminated electronic component 100 having a coil formed in a laminate 102 constituted by multiple insulator layers 104A to 104K, while FIG. 7(B) shows a plan view of the laminate 102 in FIG. 7(C) as viewed from above the insulator layer 104C. A coil pattern 106 constituting a part of the coil is formed at each specified position of the insulator layers 104C to 104I, and a land 106A is formed at one end of this coil pattern 106 and connected to the internal conduct inside a via 108.
With the aforementioned laminated electronic component 100, trying to provide a large connection area between the land 106A and via 108 as mentioned above results in a screen design where the land 106A opening is larger than the line opening (FIG. 7(A-1)). This increases the screen transmission amount and makes the print film thickness on the land 106A greater than the print film thickness on the line (FIG. 7(A-2)). Particularly in the case of a power inductor, where the line film thickness is increased for the purpose of lowering the RDC (direct-current resistance), thick film at the land and via leads to negative impact of the thickness of the internal conductor in the via. To be specific, the proportion of the internal conductor at the connection part increases when the layers are laminated and pressure-bonded, as shown in FIG. 7(C), which accounts for a number of problems such as stress cracks and shorting defects due to the connection of internal conductors at the top and bottom.
One known method to address the aforementioned problems is decreasing the screen opening ratio corresponding to the land and controlling the paste discharge volume to reduce the printed film thickness on the land 106B, as described in the laminated coil component and manufacturing method thereof in Patent Literature 2 specified below (refer to FIGS. 7(D-1) and 7(D-2)).